U.S. patent application number 14/405354 was filed with the patent office on 2015-05-07 for interference congestion control.
The applicant listed for this patent is Telefonaktiebolaget L M Ericsson (publ). Invention is credited to Billy Hogan, Patrik Karlsson, Waikwok Kwong, Torbjorn Wigren.
Application Number | 20150124593 14/405354 |
Document ID | / |
Family ID | 53006947 |
Filed Date | 2015-05-07 |
United States Patent
Application |
20150124593 |
Kind Code |
A1 |
Wigren; Torbjorn ; et
al. |
May 7, 2015 |
INTERFERENCE CONGESTION CONTROL
Abstract
The present disclosure concerns interference congestion control
in radio communication networks. Disclosed herein are methods as
well radio network nodes. A radio network node may, for example,
estimate a neighboring cell interference. The radio network node
may also detect a sudden significant increase in the estimated
neighboring cell interference. In response to detecting a sudden
significant in the estimated neighboring cell interference, the
radio network node may also transmit a message to at least one
other radio network node. This message may include an indicator
indicating to said at least one radio network node to initiate an
interference congestion control procedure. Hereby it is made
possible to allow for interference congestion control in radio
communication networks.
Inventors: |
Wigren; Torbjorn; (Uppsala,
SE) ; Karlsson; Patrik; (Stockholm, SE) ;
Kwong; Waikwok; (Solna, SE) ; Hogan; Billy;
(Sollentuna, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Telefonaktiebolaget L M Ericsson (publ) |
Stockholm |
|
SE |
|
|
Family ID: |
53006947 |
Appl. No.: |
14/405354 |
Filed: |
March 14, 2013 |
PCT Filed: |
March 14, 2013 |
PCT NO: |
PCT/SE2013/050252 |
371 Date: |
December 3, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13488187 |
Jun 4, 2012 |
|
|
|
14405354 |
|
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Current U.S.
Class: |
370/229 |
Current CPC
Class: |
H04W 92/20 20130101;
H04W 16/10 20130101; H04W 24/02 20130101; H04W 72/082 20130101;
H04W 28/0289 20130101 |
Class at
Publication: |
370/229 |
International
Class: |
H04W 72/08 20060101
H04W072/08; H04W 28/02 20060101 H04W028/02 |
Claims
1. A method for uplink interference congestion control performed by
a first radio network node serving a cell of interest, the method
comprising: estimating a neighboring cell interference, the
neighboring cell interference being induced in the cell of interest
by wireless activities in at least one other cell which is
different from the cell of interest; detecting a sudden significant
increase in the estimated neighboring cell interference; and in
response to detecting the sudden significant increase in the
estimated neighboring cell interference, transmitting a message to
at least one other radio network node that is serving at least one
cell which is different from the cell of interest, wherein the
message includes an indicator indicating to said at least one other
radio network node to initiate an interference congestion control
procedure.
2. The method according to claim 1, wherein detecting a sudden
significant increase in the estimated neighboring cell interference
comprises: determining a change in the estimated neighboring cell
interference occurring during a first time period; and establishing
that the determined change in the estimated neighboring cell
interference is above a first threshold value.
3. The method according to claim 2, wherein the length of the first
time period is in the range of 10 to 50 milliseconds.
4. The method according to claim 2, wherein the first threshold
value is in the range of 2-5 decibels.
5. The method according to claim 1, wherein estimating (310) the
neighbor cell interference comprises: estimating a load utilization
probability p.sub.load(t.sub.1) based at least on a load
utilization probability estimate {circumflex over
(p)}.sub.load(t.sub.0) and an interference-and-noise sum estimate
{circumflex over (P)}.sub.other(t.sub.0)+{circumflex over
(P)}.sub.N(t.sub.0) applicable at a time t.sub.0 to obtain a load
utilization probability estimate {circumflex over
(p)}p.sub.load(t.sub.1) applicable at a time t.sub.1, wherein
t.sub.1-t.sub.0=T>0; estimating an interference-and-noise sum
P.sub.other(t.sub.1)+P.sub.N(t.sub.1) based at least on the load
utilization probability estimate {circumflex over
(p)}.sub.load(t.sub.0) and the interference-and-noise sum estimate
{circumflex over (P)}.sub.other(t.sub.0)+{circumflex over
(P)}.sub.N(t.sub.0) to obtain an interference-and-noise sum
estimate {circumflex over (P)}.sub.other(t.sub.1)+{circumflex over
(P)}.sub.N(t.sub.1) applicable at the time t.sub.1; and estimating
an neighbor cell interference P.sub.other(t.sub.1) based at least
on the interference-and-noise sum estimate {circumflex over
(P)}.sub.other(t.sub.1)+{circumflex over (P)}.sub.N(t.sub.1) and a
thermal noise estimate {circumflex over (P)}.sub.N(t.sub.1) to
obtain a neighbor cell interference estimate P.sub.other(t.sub.1)
applicable at the time t.sub.1, wherein the load utilization
probability p.sub.load(t) expresses a relationship between radio
resource grants scheduled to one or more user equipments, UEs, and
radio resource grants used by the same UEs applicable at a time t,
each UE being a UE in the cell of interest, and the load
utilization probability estimate {circumflex over (p)}.sub.load(t)
being an estimate thereof, wherein the interference-and-noise sum
P.sub.other(t) P.sub.N(t) expresses a sum of undesired signals,
other than an own cell load P.sub.own(t), applicable at the time t,
and the interference-and-noise sum estimate {circumflex over
(P)}.sub.other(t)+{circumflex over (P)}.sub.N(t) being an estimate
thereof, wherein the own cell load P.sub.own(t) expresses a sum of
signals due to wireless activities in the cell of interest
applicable at the time t, wherein the neighbor cell interference
P.sub.other(t) expresses a sum of interferences present in the cell
of interest due to wireless activities applicable at the time t in
one or more cells other than in the cell of interest, and the
neighbor cell interference estimate {circumflex over
(P)}.sub.other(t) being an estimate thereof, and wherein a thermal
noise P.sub.N(t) expresses a sum of undesired signals present in
the cell of interest at the time t other than the own cell load
P.sub.own(t) and other than the neighbor cell interference
P.sub.other(t) and the thermal noise estimate {circumflex over
(P)}.sub.N(t) being an estimate thereof.
6. The method according to claim 1, further comprising comparing
the estimated neighboring cell interference with a second threshold
value, wherein detecting the sudden significant increase in the
estimated neighboring cell interference is performed only in
response to the estimated neighboring cell interference being above
the second threshold value.
7. The method according to claim 6, wherein the second threshold
value is in the range of 2-4 decibel over a thermal noise power
floor value.
8. A method for uplink interference congestion control performed by
a second radio network node, the method comprising: receiving, from
a first radio network node, a message including an indicator
indicating to the second radio network node to initiate an
interference congestion control procedure; in response to receiving
said message, analyzing a scheduling of one or more user
equipments, UEs, to determine a likelihood that the second radio
network node caused a sudden significant increase in an estimated
neighboring cell interference; and controlling uplink interference
congestion in dependence of the determined likelihood that the
second radio network node caused the sudden significant increase in
the estimated neighboring cell interference.
9. The method according to claim 8, wherein analyzing the
scheduling of the one or more UEs comprises: reading a history of
uplink, UL, grants for said one or more UEs from a memory of the
second radio network node, wherein the history of UL grants
includes information on the amount of UL grants scheduled during a
second time period; analyzing the history of UL grants to determine
whether an increase of the amount of scheduled UL grants has
occurred during said second time period; if it is determined that
an increase of the amount of UL grants has occurred during said
second time period comparing the detected increase of the amount of
scheduled UL grants with a third threshold value; and wherein
controlling the UL interference congestion is performed if the
detected increase of the amount of UL grants is above the third
threshold value.
10. The method according to claim 9, wherein the length of the
second time period is in the range of 10 to 50 milliseconds.
11. The method according to claim 9, wherein the third threshold
value is a value which is in the range of 30 to 60 percent of the
maximum amount of scheduled UL grants that can be assigned by the
second radio network node.
12. The method according to claim 8, wherein analyzing the
scheduling of the one or more UEs comprises: reading a history of
transmit powers of said one or more UEs from a memory of the second
radio network node, wherein the history of transmit powers includes
information on the transmit powers of said one or more UEs during a
third time period; analyzing the history of transmit powers to
determine whether an increase of transmit powers has occurred
during said third time period; if it is determined that an increase
of the transmit powers has occurred during said third time period
furthermore comparing the detected increase of the transmit powers
with a fourth threshold value; and wherein controlling the UL
interference congestion is performed if the detected increase of
the transmit powers is above the fourth threshold value.
13. The method according to claim 12, wherein the length of the
third time period is in the range of 10 to 80 milliseconds.
14. The method according to claim 12, wherein the fourth threshold
value is a value which is in the range of 5-15 dB.
15. The method according to claim 8, wherein controlling the UL
interference congestion comprises: transmitting a message to one or
more UEs, wherein said message comprises an information element
including a request to the one or more UEs to decrease the
allowable UL data rate.
16. The method according to claim 8, wherein controlling the UL
interference congestion comprises: transmitting a message to one or
more UEs, wherein said message comprises an information element
including a request to the one or more UEs to reduce the
transmission power.
17. A first radio network node for uplink interference congestion
control, comprising: a transceiver configured to transmit and
receive messages to and from at least one other radio network node
configured to serve at least one other cell which is different from
the cell of interest; and a scheduler configured to schedule uplink
transmissions from at least one user equipment, UE, wherein the
scheduler is also configured to: estimate a neighboring cell
interference, the neighboring cell interference being induced in
the cell of interest by wireless activities in at least one other
cell which is different from the cell of interest; and detect a
sudden significant increase in the estimated neighboring cell
interference; and wherein the transceiver is configured to, in
response to detecting the sudden significant increase in the
estimated neighboring cell interference, transmit a message to at
least one other radio network node that is serving at least one
cell which is different from the cell of interest, wherein the
message includes an indicator indicating to said at least one other
radio network node to initiate an interference congestion control
procedure.
18. A second radio network node for uplink interference congestion
control, comprising: a first transceiver configured to transmit and
receive messages to and from one or more user equipments, UEs; a
second transceiver configured to transmit and receive messages to
and from at least one other radio network node, and wherein the
second transceiver is also configured to receive a message from
said at least one other radio network node wherein said message
includes an indicator indicating to the second radio network node
to initiate an interference congestion control procedure; and a
scheduler configured to schedule uplink transmissions from the UEs,
wherein the scheduler is also configured to, in response to the
second transceiver receiving said message, analyze the scheduling
of one or more user equipments, UEs, to determine a likelihood that
the second radio network node caused a sudden significant increase
in an estimated neighboring cell interference; and to control
uplink interference congestion in dependence of the determined
likelihood that the second radio network node caused the sudden
significant increase in the estimated neighboring cell
interference.
Description
TECHNICAL FIELD
[0001] Embodiments presented herein generally relate to radio
communication. More particularly, the embodiments presented herein
relate to interference congestion control in radio communication
networks.
BACKGROUND
[0002] This section is intended to provide a background to the
various embodiments of the invention that are described in this
disclosure. The description herein may include concepts that could
be pursued, but are not necessarily ones that have been previously
conceived or pursued. Therefore, unless otherwise indicated herein,
what is described in this section is not prior art to the
description and/or claims of this disclosure and is not admitted to
be prior art by the mere inclusion in this section.
[0003] Recently, at least the following trends have emerged in
field of radio communication. First, mobile broadband traffic has
been exploding in radio communication networks such as Wideband
Code Division Multiple Access (WCDMA) networks. A technical
consequence of this is a corresponding increase of the interference
in these networks, or equivalently, an increase of the load.
Second, radio communication networks are becoming more
heterogeneous, with macro Radio Base Stations (RBS:s) being
supported by micro and pico RBS:s at so-called traffic hot spots.
Furthermore, home base stations (e.g., femto RBS:s) are emerging in
many networks. This puts increasing demands on inter-cell
interference management. A consequence of the above is also a
relatively large increase of the number of radio network nodes in
radio communication networks. An additional consequence is reduced
operator control. There is therefore a trend towards introducing
more self-organizing network (SON) functionality in radio
communication networks. Such functionality may support interference
management by automatic interference threshold setting and
adaptation, e.g. for a sub-set of the nodes of the cellular
network.
[0004] It is foreseen that interference may become an increasingly
important challenge to deal with in today's and future radio
communication networks as the traffic is increasing. This may for
example be the case in heterogeneous networks (also known as
HetNets).
1.1. Technical Background
[0005] 1.1.1. Load Estimation without Neighboring Cell Interference
Estimation
[0006] The following is a discussion on measurement and estimation
techniques to measure instantaneous total load on the uplink air
interface given in a radio cell of a WCDMA system. In general, a
load at the antenna connector is given by noise rise, also referred
to as Rise over Thermal, RoT(t), defined by:
RoT ( t ) = P RTWP ( t ) P N ( t ) , ( 1 ) ##EQU00001##
where P.sub.N(t) is the thermal noise level as measured at the
antenna connector. For the purposes of discussion, P.sub.RTWP(t)
may be viewed as the total wideband power defined by:
P RTWP ( t ) = i = 1 I P i ( t ) + P other ( t ) + P N ( t ) , ( 2
) ##EQU00002##
also measured at the antenna connector. The total wideband power
P.sub.RTWP(t), is unaffected by any de-spreading applied. In (2),
P.sub.other(t) represents the power as received from one or more
cells of the WCDMA system other than an own cell. The P.sub.i(t)
are the powers of the individual users. A difficulty of any RoT
estimation technique is in the inherent inability to separate the
thermal noise P.sub.N(t) from the interference P.sub.other(t) from
other cells.
[0007] Another specific challenge that generally needs to be
addressed is that the signal reference points are, by definition,
at the antenna connectors. The measurements are however obtained
after the analog signal conditioning chain, in the digital
receiver. The analog signal conditioning chain may introduce a
scale factor error of about 1 dB (1-sigma) that is generally
difficult to compensate for. Fortunately, all powers of (2) are
equally affected by the scale factor error so when (1) is
calculated, the scale factor error can be cancelled as follows:
RoT Digital Receiver ( t ) = P RTWP Digital Receiver ( t ) P N
Digital Receiver ( t ) = .gamma. ( t ) P RTWP Antenna ( t ) .gamma.
( t ) P N Antenna ( t ) = RoT Antenna ( t ) . ( 3 )
##EQU00003##
[0008] In order to understand the fundamental challenge of
interferences from other cells, i.e. neighbor cell interference,
when performing load estimation, it should be appreciated that:
P.sub.other(t)+P.sub.N(t)=E[P.sub.other(t)]+E[P.sub.N(t)]+.DELTA.P.sub.o-
ther(t)+.DELTA.P.sub.N(t). (4)
where E[ ] denotes a mathematical expectation and where A denotes a
variation around the mean. The fundamental challenge can now be
seen. Since there are no measurements available in the RBS that are
related to the other cell interference (i.e. the neighbor cell
interference), a linear filtering operation can at best estimate
the sum E[P.sub.other(t)]+E[P.sub.N(t)]. This estimate cannot be
used to deduce the value of E[P.sub.N(t)]. The situation is
generally the same as when the sum of two numbers is available.
Then there is no way to figure out the individual values of
E[P.sub.other(t)] and E[P.sub.N(t)]. It has also been formally
proved that the thermal noise power floor is not mathematically
observable.
[0009] FIG. 1 illustrates a conventional algorithm that estimates a
noise floor. The illustrated algorithm is referred to as a sliding
window algorithm, and estimates the RoT as given by equation (1)
above. This conventional estimation algorithm can provide an
accurate estimation of the thermal noise floor N(t). Since it is
generally not possible to obtain exact estimates of this quantity
due to the other cell interference (i.e. neighbor cell
interference), the estimator therefore applies an approximation, by
consideration of a soft minimum as computed over a relative long
window in time. It should be appreciated that this estimation
relies on the fact that the noise floor is constant over very long
periods of time (disregarding the small temperature drift).
[0010] A disadvantage of the sliding window algorithm is that the
algorithm generally requires a large amount of storage memory. This
may become particularly troublesome in case a large number of
instances of the algorithm is needed, as may be the case when
interference congestion is introduced in the uplink. A recursive
algorithm has been introduced to reduce the memory consumption,
e.g. as suggested in the U.S. Pat. No. 8,346,177. Relative to the
sliding window algorithm, the recursive algorithm can reduce the
memory requirement by a factor of more than one hundred.
1.1.2 Load Prediction
[0011] The following is a discussion on techniques to predict
instantaneous load on the uplink air interface ahead in time. The
scheduler uses this functionality. The scheduler tests different
combinations of grants to determine the best combinations, e.g.,
maximizing the throughput. This scheduling decision will only
affect the air interface load after a number of TTIs (each such TTI
a predetermined time duration such as 2 or 10 ms), due to grant
transmission latency and UE latency before the new grant takes
effect over the air interface.
[0012] In a conventional SIR (signal-to-interference ratio) based
method, the prediction of uplink load, for a tentative scheduled
set of UEs and grants, is based on the power relation defined
by:
P RTWP ( t ) - P N ( t ) = i = 1 N L i ( t ) P RTWP ( t ) + P other
( t ) , ( 5 ) ##EQU00004##
where L.sub.i(t) is the load factor of the i-th UE of the own cell.
As indicated, P.sub.other(t) denotes the other cell interference.
The load factors of the own cell are computed as follows. First,
note that:
( C / I ) i ( t ) = P i ( t ) P RTWP ( t ) - ( 1 - .alpha. ) P i =
L i ( t ) P RTWP ( t ) P RTWP ( t ) - ( 1 - .alpha. ) L i ( t ) P
RTWP ( t ) = L i ( t ) 1 - ( 1 - .alpha. ) L i ( t ) .revreaction.
L i ( t ) = ( C / I ) i ( t ) 1 + ( 1 - .alpha. ) ( C / I ) i ( t )
, i = 1 , , I , ( 6 ) ##EQU00005##
where I is the number of UEs in the own cell and a is the
self-interference factor. The carrier to interference values,
(C/I).sub.i(t), i=1, . . . , I, are then related to the SINR
(measured on the DPCCH channel) as follows:
( C / I ) i ( t ) = SINR i ( t ) W i RxLoss G .times. ( 1 + .beta.
DPDCH , i 2 ( t ) + .beta. EDPCCH , i 2 ( t ) + n codes , i ( t )
.beta. EDPDCH , i 2 ( t ) + .beta. HSDPCCH , i 2 ( t ) .beta. DPCCH
2 ( t ) ) , ( 7 ) i = 1 , , I . ##EQU00006##
[0013] In (7), W.sub.i represents the spreading factor, RxLoss
represents the missed receiver energy, G represents the diversity
gain and the .beta.:s represent the beta factors of the respective
channels. Here, inactive channels are assumed to have zero data
beta factors.
[0014] The UL load prediction then computes the uplink load of the
own cell by a calculation of (6) and (7) for each UE of the own
cell, followed by a summation:
L own ( t ) = i = 1 I L i ( t ) , ( 8 ) ##EQU00007##
which transforms (5) to:
P.sub.RTWP(t)=L.sub.own(t)P.sub.RTWP(t)+P.sub.othor(t)+P.sub.N(t).
(9)
[0015] Dividing (9) by P.sub.N(t) shows that the RoT can be
predicted k TTIs ahead as:
RoT ( t + kT ) = P other ( t ) / P N ( t ) 1 - L own ( t ) + 1 1 -
L own ( t ) . ( 10 ) ##EQU00008##
[0016] In the SIR based load factor calculation, the load factor
L.sub.i(t) is defined by (6). However, in a power based load factor
calculation, the load factor L.sub.i(t) can be defined by:
L i ( t ) = P i ( t ) P RTWP ( t ) , i = 1 , , I , ( 11 )
##EQU00009##
and equations (8)-(10) may be calculated based on the load factor
L.sub.i(t) of (11) to predict the RoT k TTIs ahead. An advantage of
the power based load factor calculation is that the parameter
dependency is reduced. But on the downside, a measurement of the UE
power is needed.
1.1.3 Heterogeneous Networks (HetNets)
[0017] In heterogeneous networks (HetNets), different kinds of
radio cells are generally mixed. A challenge that arises in Hetnets
in that the cells are likely to have different radio properties in
terms of (among others): [0018] radio sensitivity; [0019] frequency
band; [0020] coverage; [0021] output power; [0022] capacity; and
[0023] acceptable load level.
[0024] This can be an effect of the use of different RBS sizes
(macro, micro, pico, femto), different revisions (different
receiver technology, software quality), different vendors, the
purpose of a specific deployment, and so on. An important factor in
HetNets is therefore that of the air interface load management,
i.e., the issues associated with the scheduling of radio resources
in different cells and the interaction between cells in terms of
inter-cell interference.
[0025] These issues are exemplified with reference to FIG. 2 which
illustrates a low power cell with limited coverage intended to
serve a hotspot. To enable sufficient coverage of the hot spot, an
interference suppressing receiver like the G-rake+ is used. One
challenge is now that the low power cell is located in the interior
of and at the boundary of a specific macro cell. Also, surrounding
macro cells interfere with the low power cell rendering a high
level of other cell interference in the low power cell which,
despite the advanced receiver, reduces the coverage to levels that
do not allow coverage of the hot spot. As a result, UEs of the hot
spot are connected to the surrounding macro cells, which can
further increase the other cell interference (i.e. neighbor cell
interference) experienced by the low power cell.
SUMMARY
[0026] It is in view of the above considerations and others that
the various embodiments disclosed herein have been made.
[0027] It is a general object to provide for improved interference
congestion control. Advantageously, embodiments described in this
disclosure should allow for improved interference congestion
control in HetNets.
[0028] The various embodiments as set forth in the appended
independent claims address this general object. The appended
dependent claims represent additional advantageous embodiments.
[0029] A first non-limiting aspect of the disclosed subject-matter
is directed to a method for uplink interference congestion control.
The method is performed by a first radio network node serving a
cell of interest. The method may comprise estimating a neighboring
cell interference, the neighboring cell interference being induced
in the cell of interest by wireless activities in at least one
other cell which is different from the cell of interest. Also, the
method may comprise detecting a sudden significant increase in the
estimated neighboring cell interference. In response to detecting
the sudden significant increase in the estimated neighboring cell
interference, the method may additionally comprise transmitting a
message to at least one other radio network node that is serving at
least one cell which is different from the cell of interest. This
message includes an indicator indicating to said at least one other
radio network node to initiate an interference congestion control
procedure.
[0030] In one embodiment, detecting a sudden significant increase
in the estimated neighboring cell interference comprises
determining a change in the estimated neighboring cell interference
occurring during a first time period; and establishing that the
determined change in the estimated neighboring cell interference is
above a first threshold value. The first threshold value may be a
value, which is positive (i.e. the threshold value has a positive
sign). In other words, the first threshold value may be a
non-negative value.
[0031] The length of the first time period may e.g. be in the range
of 10 to 50 milliseconds. That is, the first time period may for
example be 10 milliseconds, 15 milliseconds, 20 milliseconds, 25
milliseconds, 30 milliseconds, 35 milliseconds, 40 milliseconds, 45
milliseconds, or 50 milliseconds.
[0032] Also, the first threshold value may be in the range of 2-5
decibels (dB). That is, the first threshold value may e.g. be 2 dB,
2.5 dB, 3 dB, 3.5 dB, 4 dB, 4.5 dB, or 5 dB.
[0033] In another embodiment, detecting a sudden significant
increase in the estimated neighboring cell interference may
comprise detecting whether an increase of a neighboring cell
interference has occurred during a first time period, and also
determining that a sudden significant increase in the estimated
neighboring cell interference has occurred when said increase of
the neighboring cell interference is above a first threshold.
[0034] The length of the first time period may e.g. be in the range
of 10 to 50 milliseconds. That is, the first time period may for
example be 10 milliseconds, 15 milliseconds, 20 milliseconds, 25
milliseconds, 30 milliseconds, 35 milliseconds, 40 milliseconds, 45
milliseconds, or 50 milliseconds.
[0035] Also, the first threshold value may be in the range of 2-5
decibels (dB). That is, the first threshold value may e.g. be 2 dB,
2.5 dB, 3 dB, 3.5 dB, 4 dB, 4.5 dB, or 5 dB.
[0036] Advantageously, estimating the neighboring cell interference
may be performed in accordance with the unpublished U.S. patent
application Ser. No. 13/488,187, which was filed on Jun. 4, 2012.
The unpublished US patent application is incorporated herein by
reference to Appendix A. For example, estimating the neighbor cell
interference may thus comprise estimating a load utilization
probability p.sub.load(t.sub.1) based at least on a load
utilization probability estimate {circumflex over
(p)}.sub.load(t.sub.0) and an interference-and-noise sum estimate
{circumflex over (P)}.sub.other(t.sub.0)+{circumflex over
(P)}.sub.N(t.sub.0) applicable at a time t.sub.0 to obtain a load
utilization probability estimate {circumflex over
(p)}.sub.load(t.sub.1) applicable at a time t.sub.1, wherein
t.sub.1-t.sub.0=T>0. The method may also comprise estimating an
interference-and-noise sum P.sub.other(t.sub.1)+P.sub.N(t.sub.1)
based at least on the load utilization probability estimate
{circumflex over (p)}.sub.load(t.sub.0) and the
interference-and-noise sum estimate {circumflex over
(P)}.sub.other(t.sub.0)+{circumflex over (P)}.sub.N(t.sub.0) to
obtain an interference-and-noise sum estimate {circumflex over
(P)}.sub.other(t.sub.1)+{circumflex over (P)}.sub.N(t.sub.1)
applicable at the time t.sub.1. The method may further comprise
estimating an neighbor cell interference P.sub.other(t.sub.1) based
at least on the interference-and-noise sum estimate {circumflex
over (P)}.sub.other(t.sub.1)+{circumflex over (P)}.sub.N(t.sub.1)
and a thermal noise estimate {circumflex over (P)}.sub.N(t.sub.1)
to obtain a neighbor cell interference estimate {circumflex over
(P)}.sub.other(t.sub.1) applicable at the time t.sub.1.
[0037] The load utilization probability p.sub.load(t) may express a
relationship between radio resource grants scheduled to one or more
user equipments, UEs, and radio resource grants used by the same
UEs applicable at a time t. Each UE may be a UE in the cell of
interest, and the load utilization probability estimate {circumflex
over (p)}.sub.load(t) may express an estimate of the load
utilization p.sub.load(t). Furthermore, the interference-and-noise
sum P.sub.other(t)+P.sub.N(t) may express a sum of undesired
signals, other than an own cell load P.sub.own(t) applicable at the
time t, and the interference-and-noise sum estimate {circumflex
over (P)}.sub.other(t)+{circumflex over (P)}.sub.N(t) being an
estimate thereof. Also, the own cell load P.sub.own(t) may express
a sum of signals due to wireless activities in the cell of interest
applicable at the time t. Moreover, the neighbor cell interference
P.sub.other(t) may express a sum of interferences present in the
cell of interest due to wireless activities applicable at the time
t in one or more cells other than in the cell of interest, and the
neighbor cell interference estimate {circumflex over
(P)}.sub.other(t) being an estimate thereof. Still further, a
thermal noise P.sub.N(t) may express a sum of undesired signals
present in the cell of interest at the time t other than the own
cell load P.sub.own(t) and other than the neighbor cell
interference P.sub.other(t), and the thermal noise estimate
{circumflex over (P)}.sub.N(t) being an estimate thereof.
[0038] In one embodiment, the method may additionally comprise
comparing the estimated neighboring cell interference with a second
threshold value. If so, detecting the sudden significant increase
in the estimated neighboring cell interference may be performed
only in response to the estimated neighboring cell interference
being above the second threshold value. The second threshold value
may e.g. be in the range of 2-4 decibel over a thermal noise power
floor value, i.e. for example 2, 2.5, 3, 3.5 or 4 dB over the
thermal noise power floor value.
[0039] A second non-limiting aspect of the disclosed subject-matter
is also directed to a method for uplink interference congestion
control. The method is performed by a second radio network node.
The method may comprise receiving, from a first radio network node,
a message including an indicator indicating to the second radio
network node to initiate an interference congestion control
procedure. In response to receiving said message, the method may
also comprise analyzing a scheduling of one or more user
equipments, UEs, to determine a likelihood that the second radio
network node caused a sudden significant increase in an estimated
neighboring cell interference. Furthermore, the method may comprise
controlling uplink interference congestion in dependence of the
determined likelihood that the second radio network node caused the
sudden significant increase in the estimated neighboring cell
interference.
[0040] In one embodiment, analyzing the scheduling of the one or
more UEs may comprise: reading a history of uplink, UL, grants for
said one or more UEs from a memory of the second radio network
node, wherein the history of UL grants includes information on the
amount of UL grants scheduled during a second time period;
analyzing the history of UL grants to determine whether an increase
of the amount of scheduled UL grants has occurred during said
second time period; if it is determined that an increase of the
amount of UL grants has occurred during said second time period
comparing the detected increase of the amount of scheduled UL
grants with a third threshold value. The controlling of the UL
interference congestion may be performed if the detected increase
of the amount of UL grants is above the third threshold value.
[0041] The length of the second time period may be in the range of
10 to 80 milliseconds. That is, the length of the second time
period may e.g. be 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,
70, 75 or 80 milliseconds.
[0042] Also, the third threshold value may be a value which is in
the range of 30-60 percent of the maximum amount of scheduled UL
grants that can be assigned by the second radio network node.
[0043] In another embodiment, analyzing the scheduling of the one
or more UEs may comprise reading a history of transmit powers of
said one or more UEs from a memory of the second radio network
node, wherein the history of transmit powers includes information
on the transmit powers of said one or more UEs during a third time
period; analyzing the history of transmit powers to determine
whether an increase of transmit powers has occurred during said
third time period; if it is determined that an increase of the
transmit powers has occurred during said third time period
furthermore comparing the detected increase of the transmit powers
with a fourth threshold value. The controlling of the UL
interference congestion may be performed if the detected increase
of the transmit powers is above the fourth threshold.
[0044] The length of the third time period may be in the range of
10 to 80 milliseconds. That is, the length of the second time
period may e.g. be 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,
70, 75 or 80 milliseconds.
[0045] Also, the fourth threshold value is a value which is in the
range of 5-15 decibel. For example, the fourth threshold value may
be 5, 10 or 15 db.
[0046] In some embodiments, controlling the UL interference
congestion may comprise transmitting a message to one or more UEs,
wherein said message comprises an information element including a
request to the one or more UEs to decrease the allowable UL data
rate.
[0047] In some embodiments, controlling the UL interference
congestion may additionally, or alternatively, comprise
transmitting a message to one or more UEs, wherein said message
comprises an information element including a request to the one or
more UEs to reduce the transmission power.
[0048] A third non-limiting aspect of the disclosed subject-matter
is directed to a first radio network node for uplink interference
congestion control. The first radio network node may comprise a
transceiver configured to transmit and receive messages to and from
at least one other radio network node configured to serve at least
one other cell which is different from the cell of interest. Also,
a scheduler may be configured to schedule uplink transmissions from
at least one user equipment, UE. The scheduler may further be
configured to: estimate a neighboring cell interference, the
neighboring cell interference being induced in the cell of interest
by wireless activities in at least one other cell which is
different from the cell of interest; and detect a sudden
significant increase in the estimated neighboring cell
interference. Moreover, the transceiver may be configured to, in
response to detecting the sudden significant increase in the
estimated neighboring cell interference, transmit a message to at
least one other radio network node that is serving at least one
cell which is different from the cell of interest. This message may
include an indicator indicating to said at least one radio network
node to initiate an interference congestion control procedure.
[0049] A fourth non-limiting aspect of the disclosed subject-matter
is directed to a second radio network node for uplink interference
congestion control. The second radio network node may comprise a
first transceiver configured to transmit and receive messages to
and from one or more user equipments, UEs. A second transceiver is
configured to transmit and receive messages to and from at least
one other radio network node, wherein the second transceiver is
also configured to receive a message from said at least one other
radio network node wherein said message includes an indicator
indicating to the second radio network node to initiate an
interference congestion control procedure. Furthermore, a scheduler
is configured to schedule uplink transmissions from the UEs. The
scheduler is also configured to, in response to the second
transceiver receiving said message, analyze the scheduling of one
or more user equipments, UEs, to determine a likelihood that the
second radio network node caused a sudden significant increase in
an estimated neighboring cell interference. The scheduler is also
configured to control uplink interference congestion in dependence
of the determined likelihood that the second radio network node
caused the sudden significant increase in the estimated neighboring
cell interference.
[0050] A fifth non-limiting aspect of the disclosed subject matter
is directed to a computer-readable medium which has stored therein
programming instructions. When a computer executes the programming
instructions, the computer executes the method of the herein
described first aspect.
[0051] A sixth non-limiting aspect of the disclosed subject matter
is directed to a computer-readable medium which has stored therein
programming instructions. When a computer executes the programming
instructions, the computer executes the method of the herein
described second aspect.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] These and other aspects, features and advantages will be
apparent and elucidated from the following description of various
embodiments, reference being made to the accompanying drawings, in
which:
[0053] FIG. 1 illustrates a conventional algorithm that estimates a
noise floor;
[0054] FIG. 2 illustrates an example scenario of a low power cell
with limited coverage intended to serve a hotspot;
[0055] FIG. 3 shows a flowchart of a method according to an
embodiment performed in a first radio network node;
[0056] FIG. 4 shows flowcharts of example methods for detecting a
sudden increase of a neighboring cell interference:
[0057] FIG. 5 illustrates various message formats that may be used
in signals or data messages, which are signaled when executing
methods according to the various embodiments disclosed herein.
[0058] FIG. 6 shows a flowchart of a method according to an
embodiment performed in a second radio network node;
[0059] FIG. 7 shows a flowchart of an example method of performing
UE scheduling analysis;
[0060] FIG. 8 shows a flowchart of an example method of performing
UE scheduling analysis;
[0061] FIG. 9 shows a flowchart of a method for interference
control;
[0062] FIG. 10 shows a flowchart of a method for interference
control;
[0063] FIG. 11 shows an example embodiment of a first radio network
node;
[0064] FIG. 12 shows another example embodiment of a first radio
network node;
[0065] FIG. 13 shows an example embodiment of a second radio
network node; and
[0066] FIG. 14 shows another example embodiment of a second radio
network node.
DETAILED DESCRIPTION
[0067] The invention will now be described more fully hereinafter
with reference to the accompanying drawings, in which certain
embodiments are shown. The invention may, however, be embodied in
many different forms and should not be construed as limited to the
embodiments set forth herein; rather, these embodiments are
provided by way of example so that this disclosure will be thorough
and complete, and will fully convey the scope of the invention to
those persons skilled in the art. Like reference numbers refer to
like elements or method steps throughout the description.
[0068] In this disclosure, 3GPP technologies (e.g. WCDMA) are used
as example technologies for explanation purposes. It should however
be appreciated that the technology described herein could be
applied in non-3GPP technologies as well, e.g. WiMax, etc. Thus,
the scope of this disclosure should not be interpreted as being
limited to 3GPP technologies such as WCDMA. Also, as used in this
disclosure, the term "user equipment (UE)" is used to mean any
device, which can be used by a user to communicate. Also, the term
UE may be referred to as a mobile terminal, a terminal, a user
terminal (UT), a wireless terminal, a wireless communication
device, a wireless transmit/receive unit (WTRU), a mobile phone, a
cell phone, etc. Yet further, the term UE includes MTC (Machine
Type Communication) devices, which do not necessarily involve human
interaction. Also, the term "radio network node" as used herein
generally denotes a point (e.g. a fixed point) being capable of
communicating with the UE. As such, it may be referred to as a base
station, a radio base station, a NodeB or an evolved NodeB (eNB),
access point, relay node, etcetera.
[0069] As indicated hereinabove, a potential disadvantage of many
conventional RoT(t) estimation techniques lies in the difficulty in
separating the thermal noise P.sub.N(t) from the interference
P.sub.other(t) from other cells, i.e. neighboring cells. This
generally makes it difficult to estimate the RoT(t), i.e., it is
generally difficult to estimate the load as given in equation (1).
The other cell interference P.sub.other(t) in this context may be
viewed as a sum of interferences present in a cell of interest due
to wireless activities applicable at time t in one or more cells
other than in the cell of interest. Therefore, as used throughout
this disclosure (including Appendix A) will sometimes also be
referred to as "neighbor cell interference" or "neighboring cell
interference". In one or more aspects, the determination of the
neighbor cell interference P.sub.other(t) involves estimating the
neighbor cell interference. For the purposes of this disclosure,
estimations of parameters are indicated with a " " (caret)
character. For example, {circumflex over (P)}.sub.other(t) may be
read as an estimate of the other cell interference P.sub.other(t),
i.e. the neighbor cell interference P.sub.other(t).
[0070] There exist known techniques to determine the neighbor cell
interference estimate {circumflex over (P)}.sub.other(t). These
conventional techniques generally assume that the powers of all
radio links are measured in the uplink receiver. This assumption
may not necessarily be true in all instances today. The power
measurement is associated with difficulties since, e.g.: [0071] In
WCDMA for example, the uplink transmission is not necessarily
orthogonal, which can cause errors when the powers are estimated;
and [0072] The individual code powers are often small, making the
SNRs (signal-to noise ratio) low as well. This further contributes
to a potential inaccuracy of the power estimates.
[0073] One challenge associated with the conventional neighbor cell
interference estimation techniques is that the sum of other cell
interference and thermal noise P.sub.other(t)+P.sub.N(t) (referred
to as the interference-and-noise sum) generally need to be
estimated through high order Kalman filtering. The primary reason
for this is that all powers of the UEs need to be separately
filtered using at least one Kalman filter state per UE when such
techniques are used. This step is consequently associated with a
relatively high computational complexity. There exist techniques
that can reduce this computational complexity, but the complexity
may be still too high when the number of UEs increases. In these
conventional solutions, the thermal noise floor N(t) is estimated
as described above, i.e., {circumflex over (N)}(t) is determined
followed by a subtraction to arrive at an estimate of the other
cell interference {circumflex over (P)}.sub.other(t).
[0074] In the existing solutions, the EUL (Enhanced Uplink)
utilizes a scheduler that aims to fill the load headroom of the air
interface, so that the different UE requests for bitrates are met.
As stated above, the air-interface load in WCDMA is determined in
terms of the noise rise over the thermal power level, i.e., the
RoT(t), which is estimated at the base station.
[0075] Regarding HetNets in particular, challenges associated with
conventional scheduling techniques can be explained in a relatively
straightforward manner. For scheduling in the radio network node in
general, existing known techniques require measurement of all UE
powers in the UL. This may be costly computationally, requiring
Kalman filters of high order for processing the measurements to
obtain estimates of the neighboring cell interference power. This
is because each own cell UE adds a state to the Kalman filter. The
consequence, if such estimation cannot be done, is that the
scheduler is generally unaware of the origin of the interference,
thereby making it more difficult to arrive at good scheduling
decisions. For HetNets, the problem is again that there is no
information of the origin of interference, and interference
variance, for adjacent (e.g. neighboring) cells. This is primarily
due to the lack of low complexity estimators for these quantities.
Consequently, in HetNets where it is foreseen that interference may
become an increasingly important challenge, there is a need to
allow for improved, or alternative, ways of controlling
interference congestion.
[0076] Each of one or more aspects of the disclosed subject matter
addresses one or more of the issues related to conventional
techniques.
[0077] With reference to FIG. 3, an example embodiment of a method
for uplink interference congestion control is shown. The method may
be performed by, or otherwise implemented in, a first radio network
node serving a cell of interest.
[0078] As illustrated, in step 310, neighboring cell interference
is estimated. The neighboring cell interference is induced in the
cell of interest (i.e. the radio cell controlled by the first radio
network node) by wireless activities in one or several other cells,
which are different from the cell of interest.
[0079] Estimating neighbor cell interference can be performed in
various ways. For the purpose of this disclosure but without
limitation, techniques for estimating neighbor cell interference
may advantageously have the following characteristics: [0080]
Perform measurements of the received UL total wideband power
(RTWP); [0081] Perform measurements of the load utilization of the
UL, or alternatively, the actual used load factor; [0082] Estimate
at least the neighboring cell interference power and the load
utilization probability
[0083] The RTWP measurement has been explained in the background
section as has the concepts of own and neighbor cell interference
power. To explain the load utilization concept, it is noted that in
WCDMA EUL (Enhanced Uplink) the scheduler gives grants to UEs.
These grants give the UEs the right to transmit with a certain rate
and power. The UE does however not have to use the grants. This
freedom of the UE may create challenges for the estimation of
uplink load. The reason is that in practice, field trials reveal a
load utilization that is sometimes less than 25%. Unless accounted
for, the scheduler may believe that the load is then much higher
than it actually is. The result of this is that the scheduler stops
granting too early, resulting in under-utilization of the UL. Such
waste is not desirable.
[0084] Therefore, it is instead proposed to account for the
measured utilization in the estimation of interference powers, like
neighbor cell interference. This can be done as explained in the
unpublished U.S. patent application Ser. No. 13/488,187,
incorporated herein by reference to Appendix A. In U.S. patent
application Ser. No. 13/488,187, the estimated neighbor cell
interference is made dependent on an additional estimate of the
load utilization. This estimate may be supported by a measurement
relatively closely related to the estimated load utilization. This
way, the accuracy of the neighbor cell interference power estimate
can be improved. Secondly, the availability of these measurements
at TTI (Transmission-Time-Interval) rate, together with the
improved accuracy of the estimates, may allow for a relatively high
bandwidth of the estimates. Since the estimates are generally more
accurate, less filtering is needed for, e.g., smoothing and noise
suppression, which in turn may enhance the bandwidth.
[0085] Estimating 310 the neighboring cell interference may, thus,
advantageously (but not necessarily) be performed in accordance
with one or more of the embodiments disclosed in U.S. patent
application Ser. No. 13/488,187, see Appendix A. Since these
embodiments are detailed in Appendix A, these embodiments will not
be further detailed here.
[0086] With further reference to FIG. 3, the method may also
comprise detecting 320 a sudden significant increase in the
estimated neighboring cell interference as is illustrated in FIG.
3. If no sudden increase is detected in step 320, the first radio
network node may continue estimating the neighboring cell
interference. This can be done at regular intervals or
continuously. However, in response to detecting 320 a sudden
significant increase in the estimated neighboring cell
interference, a message is transmitted (i.e. sent) 330 to one or
more neighboring radio network nodes that are serving other cells,
i.e. cells that are different from the cell of interest served by
the first radio network node. The message includes an indicator
that indicates (to said other radio network nodes) to initiate an
interference congestion control procedure.
[0087] With reference to FIGS. 4A and 4B, two example embodiments
of detecting 320 a sudden significant increase in the estimated
neighboring cell interference will be described in more detail.
Turning first to FIG. 4A, in a first step 321, it can be determined
whether a change in the estimated neighboring cell interference
occurs during a first time period. If a change in the estimated
neighboring cell interference is determined 321, or detected, the
method continues to step 322. In step 322, it is established
whether or not the determined change is above a first threshold
value. The first threshold value may be a value, which is positive
(i.e. the threshold value has a positive sign). In other words, the
first threshold value may be a non-negative value. Consequently, if
a change occurs during the first time period and if this change is
also above a certain first threshold value then it can be
determined, or concluded, that a sudden increase of the neighboring
cell interference has occurred.
[0088] To this end, it should be appreciated that the exact values
of the first time period and the first threshold value should be
evaluated and tested in each specific case such that suitable
values are selected depending on specific needs, e.g. needs
regarding desired performance, etc. Important here is to select
values that are suitable for determining that a detected increase
of the estimated neighboring cell interference is sudden. As a mere
example, the first time period may be selected to be 30
milliseconds and the first threshold may be selected to be 3 dB.
Other combinations of values for the first time period and the
first threshold are of course also conceivable. It is proposed that
the first time period has a length that is 10, 15, 20, 25, 30, 35,
40, 45 or 50 milliseconds. Also, it is advantageous that the first
threshold is 2, 2.5, 3, 3.5, 4, 4.5 or 5 dB.
[0089] Turning now to the alternative embodiment illustrated in
FIG. 4B, in a first step 323, it is detected whether an increase of
neighboring cell interference has occurred during a first time
period. Subsequently, in step 325, it is determined, or concluded,
that a sudden significant increase in the estimated neighboring
cell interference has occurred when it has been determined (or,
detected), in step 324, that said increase of the neighboring cell
interference is above a first threshold. In other words, if an
increase occurs during the first time period and if this increase
is also above a certain first threshold then it can be determined,
or concluded, that a sudden increase of the neighboring cell
interference has occurred. Again, it should be appreciated that the
exact values of the first time period and the first threshold value
should be evaluated and tested in each specific case such that
suitable values are selected depending on specific needs, e.g.
needs regarding desired performance, etc. Important here is to
select values that are suitable for determining that a detected
increase of the estimated neighboring cell interference is sudden.
As a mere example, the first time period may be selected to be 30
milliseconds and the first threshold may be selected to be 3 dB. In
other words, if an increase of neighboring cell interference is
detected during a first time period of 30 milliseconds (in step
323) and if it is determined that this increase is above 3 dB (in
step 324), then it is determined that the increase of the
neighboring cell interference is sudden. Other combinations of
values for the first time period and the first threshold are of
course also conceivable. It is proposed that the first time period
has a length that is 10, 15, 20, 25, 30, 35, 40, 45 or 50
milliseconds. Also, it is advantageous that the first threshold is
2, 2.5, 3, 3.5, 4, 4.5 or 5 dB.
[0090] According to yet another example embodiment, the following
equation can be used for detecting whether an increase in the
estimated neighboring cell interference is sudden:
{circumflex over (P)}.sub.neighbor(t|t)-{circumflex over
(P)}.sub.neighbor(t-.DELTA.t|t-.DELTA.t)>threshold.sub.1
(12)
where the time period .DELTA.t fulfils .DELTA.t>0.
[0091] Turning back to FIG. 3, in response to detecting 320 a
sudden significant increase in the estimated neighboring cell
interference, a message can be transmitted, in step 330, to one or
more neighboring radio network nodes that are serving other,
neighboring, cells. With reference to FIG. 5, various possible
message formats of the message are schematically illustrated. In
one embodiment as illustrated in FIG. 5A, the message 500 comprises
and indicator 510, which is used to indicate (to receiving radio
network nodes) that the receiving radio network node(s) should
initiate an interference congestion control procedure. This
interference congestion control procedure will be further detailed
hereinbelow.
[0092] FIG. 5B illustrates an alternative message format, or
structure. In this embodiment, the message 500 additionally
comprises one information element 510 comprising the indicator and
another, additional, information element 511 comprising an
identification (ID) of the cell of interest, i.e. the radio cell
served by the first radio network node.
[0093] FIG. 5C illustrates another alternative message format, or
structure. In this embodiment, the message 500 optionally comprises
any one or both of information elements 512 and 513. In this
example, the information element 512 comprises information about
P.sub.neighbor(t|t) and the information element 513 comprises
information about {circumflex over (P)}.sub.own(t|t).
[0094] FIG. 5D illustrates yet another alternative message format,
which embodies a combination of the message formats shown in FIGS.
5B and 5C.
[0095] In still further embodiments, it is not necessary to utilize
an explicit indicator 510. Instead, the indicator 510 may be either
of or both of {circumflex over (P)}.sub.neighbor(t|t) and
{circumflex over (P)}.sub.own(t|t), see FIGS. 5E-5G. The messages
illustrated in FIGS. 5E-5G may optionally also comprise an
information element 511 (nor shown) including the above-mentioned
ID of the cell of interest.
[0096] In one embodiment, the method may optionally comprise an
additional step 340. In optional step 340, an estimated neighboring
cell interference is compared with a second threshold value. In
such embodiment, the detection 320 is only performed if, or when,
the estimated neighboring cell interference is above the second
threshold value. The second threshold value may e.g. be in the
range of 2-4 decibel over a thermal noise power floor value, i.e.
for example 2, 2.5, 3, 3.5 or 4 dB over the thermal noise power
floor value.
[0097] Turning now to FIG. 6, an example embodiment of a method for
uplink interference congestion control is shown. The method may be
performed by, or otherwise implemented in, a second radio network
node. In step 610, a message 500 (see FIG. 5) is received from a
first radio network node. This message 500 comprises at least an
indicator indicating to the second radio network node that it
should initiate an interference congestion control procedure. In
other words, the second radio network node can be said to be
informed, by the first radio network node, that the first radio
network node has experienced or otherwise detected a sudden
significant increase in its neighbor cell interference. However,
the first radio network node cannot, generally, conclude which
neighboring cell that is contributing to this sudden significant
increase of its experienced neighbor cell interference. Therefore,
the first radio network node broadcasts, or signals, the message
500 to one or several surrounding second radio network nodes,
thereby requesting these second radio network nodes to initiate an
interference congestion control procedure.
[0098] In response to receiving a message 500, the second radio
network node may analyze 620 the scheduling of one or UEs to
determine a likelihood that this second radio network node caused
the sudden increase in the estimated neighboring cell
interference.
[0099] Depending on the determined likelihood that the second radio
network node caused the sudden increase in the estimated
neighboring cell interference, the second radio network node may or
may not take measures for controlling 630 any interference caused
by the second radio network node. That is, any uplink interference
congestion can be controlled 630 in dependence of the determined
likelihood that the second radio network node caused the sudden
significant increase in the estimated neighboring cell
interference. For example, if it is determined that there is a high
likelihood that the second radio network node caused the sudden,
potentially also significant, increase in estimated neighbor cell
interference experienced by the first radio network node, then the
second radio network node will initiate a interference congestion
control procedure, thus, controlling the UL interference
congestion. On the other hand, if it is determined that there is a
low likelihood that the second radio network node caused the
sudden, potentially also significant, increase in estimated
neighbor cell interference experienced by the first radio network
node, then the second radio network node does not have to initiate
any interference congestion control procedure.
[0100] There exist various ways of performing the UE scheduling
analysis 620. FIG. 7 shows a first example process of UE scheduling
analysis 620. In step 621, the second radio network node may read a
history of uplink, UL, grants for one or more UEs. This
information, i.e. the history of UL grants, may e.g. be read or
otherwise retrieved from a memory of the second radio network node.
Generally speaking, the history of UL grants includes information,
or data, relating to the amount of UL grants that have been
scheduled by the second radio network node during a second time
period. It is readily understood that the second radio network node
should advantageously read the history of UL grants during a second
time period which corresponds to the first time period when the
first radio network node experienced the sudden significant
increase of increased interference. For example, the absolute
length of this second time period may be 10-50 milliseconds (e.g.
10, 20, 30, 40 or 50 milliseconds). That is, the second time period
may advantageously correspond (in length) to the earlier-mentioned
first time period. As will be readily understood, there is
typically a delay in the signaling between the first and the second
radio network nodes. This delay is typically around 0-30
milliseconds. Therefore, it should also be appreciated that it may
be advantageous to set the starting time of the second time period
such that any such delay is compensated for.
[0101] Subsequently, the history of UL grants can be analyzed 622
to determine whether an increase of the amount of scheduled UL
grants has occurred during the above-mentioned second time period.
If it is determined that an increase of the amount of UL grants has
occurred during said second time period, this detected increase of
the amount of scheduled UL grants is compared with a third
threshold value. The third threshold value should be evaluated and
tested in each specific case such that a suitable value is selected
depending on specific needs, e.g. needs regarding desired
performance, etc. For example, the third threshold value may be a
value which is in the range of 30-60 percent of the maximum amount
of scheduled UL grants that can be assigned by the second radio
network node.
[0102] If, or when, a detected increase of the amount of UL grants
is determined to be above the third threshold value, the method
continues to step 630 (see FIG. 6) where the second radio network
node controls the UL interference congestion.
[0103] FIG. 8 shows another example process of a UE scheduling
analysis 620. In step 623, the second radio network node may read a
history of transmit powers of one or more UEs. The history may be
read or otherwise retrieved from a memory of the second radio
network node. The history of transmit powers includes information,
or data, on the transmit powers of said one or more UEs during a
third time period. It is readily understood that the second radio
network node should advantageously read the history of transmit
powers during a second time period which corresponds to the first
time period when the first radio network node experienced the
sudden significant increase of increased interference. For example,
the absolute length of this second time period may be 10-50
milliseconds (e.g. 10, 20, 30, 40 or 50 milliseconds). That is, the
second time period may advantageously correspond (in length) to the
earlier-mentioned first time period. As will be readily understood,
there is typically a delay in the signaling between the first and
the second radio network nodes. This delay is typically around 0-30
milliseconds. Therefore, it should also be appreciated that it may
be advantageous to set the starting time of the second time period
such that any such delay is compensated for.
[0104] Subsequently, the history of transmit powers can be analyzed
624 to determine whether an increase of transmit powers has
occurred during said third time period. If it is determined that an
increase of the transmit powers has occurred during said third time
period, this increase of transmit powers is compared with a fourth
threshold value. For example, the fourth threshold value may be a
value which is in the range of 5-15 dB.
[0105] If, or when, if it is determined that an increase of the
transmit powers is above the fourth threshold value, the method
continues to step 630 (see FIG. 6) where the second radio network
node controls the UL interference congestion.
[0106] Turning back to FIG. 6, there are also various ways of
performing the control of the UL interference congestion 630. In
one embodiment, which is illustrated in FIG. 9, the second radio
network node transmits 631 a message to one or more UEs, wherein
said message comprises an information element including a request
to the one or more UEs to decrease the allowable UL data rate. In
another embodiment, which is illustrated in FIG. 10, the second
radio network transmits 632 a message to one or more UEs, wherein
said message comprises an information element including a request
to the one or more UEs to reduce the transmission power. These two
example procedures, i.e. FIGS. 9 and 10, can also be combined. By
performing the control of the UL interference congestion, those
second radio network node(s) that have determined that there is a
relatively high likelihood that these second radio network node(s)
caused the sudden increase in the neighbor cell interference
(experienced by the first radio network node) can take appropriate
measures in an attempt to reduce its/their impact of the
interference congestion. By controlling of the UL interference
congestion in this way, the impact of those second radio network
node(s) that most likely caused the sudden significant increase in
interference can reduce the impact of the interference and, hence,
the first radio network node may eventually experience a normal
interference level again.
[0107] The various embodiments described hereinabove may provide
for coordinated congestion control of interference originating in
one or more radio cells and affecting other, neighboring, radio
cells. A radio network node which experiences neighbor cell
interference may estimate the experienced neighbor cell
interference, detect a sudden significant increase in the neighbor
cell interference and signal, i.e. transmit, a message including an
indicator to indicate this fact to neighboring radio network nodes.
Upon receipt of a message including this indicator, one or a group
of neighboring radio network nodes can analyze, check or otherwise
investigate if their radio cells may be the potential cause of the
sudden significant increase of the neighbor cell interference. If a
radio network node determines that it is likely that this radio
network node (or, rather wireless activities in cells served by
this radio network node) caused the sudden significant increase of
the neighbor cell interference, this radio network node can take
appropriate measures to eliminate, alleviate or at least reduce its
impact on the interference.
[0108] An advantage with some embodiments disclosed herein is that
the proposed estimation of the neighbor cell interference is
sufficiently accurate and has a sufficiently high bandwidth to
enable a fast detection of the sudden significant increase of the
neighbor cell interference, such as when new and strong neighbor
cell interference occurs. It is another advantage with some of the
embodiments herein that a radio network node can signal, or
broadcast, messages to other neighboring radio network nodes that
it experiences a sudden significant increase in interference. This
allows for a coordinated congestion control of the interference
among the various radio network nodes in a communication network.
This may be particularly appealing in communication networks such
as HetNets. It is a further advantage of some embodiments that a
relatively fast detection of the sudden significant increase of the
neighbor cell interference allows for a relatively quick
coordinated congestion control among the various radio network
nodes of the communication network.
[0109] FIG. 11 illustrates an example embodiment of a first radio
network node 10. The first radio network node may be configured to
perform any of the methods disclosed herein with respect to FIGS. 3
and 4. The first radio network node may comprise several devices,
units, modules or circuits. In the illustrated example embodiment
of FIG. 11, the first radio network node 10 comprises a controller
11, a first transceiver 12, a second transceiver 13 and a scheduler
14. The transceiver 12 may be configured to wirelessly communicate
with wireless terminals, such as UEs. The transceiver 13 may be
configured to communicate with other radio network nodes and/or
with core network nodes. Furthermore, the controller 11 may be
configured to control the overall operations of the radio network
node 10. FIG. 11 provides a logical view of an example radio
network node 10. It is not strictly necessary that each device, or
unit, is implemented as physically separate devices, or units. Some
or all of the illustrated units may be implemented in a physical
module. Alternatively, one or more units may be implemented in
multiple physical modules as schematically illustrated in FIG.
12.
[0110] More specifically, and in accordance with one of its
non-limiting aspects, the transceiver 12 may be configured to
transmit and receive messages to and from at least one other radio
network node configured to serve at least one other cell which is
different from the cell of interest that is served by the first
radio network node 10. Furthermore, the scheduler 14 may be
configured to schedule UL transmissions from one or several UEs.
The scheduler 14 is also configured to estimate a neighboring cell
interference, the neighboring cell interference being induced in
the cell of interest by wireless activities in at least one other
cell which is different from the cell of interest. The scheduler 14
is further configured to detect a sudden significant increase in
the estimated neighboring cell interference. Yet further, the
transceiver 13 is configured to, in response to the scheduler 14
detecting the sudden significant increase in the estimated
neighboring cell interference, transmit a message to at least one
other radio network node that is serving at least one cell which is
different from the cell of interest. The message includes an
indicator indicating to said at least one other radio network node
to initiate an interference congestion control procedure.
[0111] The scheduler 14 may be further configured to determine a
change in the estimated neighboring cell interference occurring
during a first time period, and also establishing that the
determined change in the estimated neighboring cell interference is
above a first threshold value. The length of the first time period
may e.g. be in the range of 10-50 milliseconds, as described
hereinabove. Also, the first threshold value may be in the range of
2-5 decibels (dB), as described hereinabove.
[0112] Additionally, or alternatively, the scheduler 14 may be
configured to detect whether an increase of a neighboring cell
interference has occurred during a first time period, and also
determine that a sudden significant increase in the estimated
neighboring cell interference has occurred when said increase of
the neighboring cell interference is above a first threshold. The
length of the first time period may e.g. be in the range of 10-50
milliseconds, as described hereinabove. Also, the first threshold
value may be in the range of 2-5 decibels (dB), as described
hereinabove.
[0113] The scheduler 14 may furthermore be configured to estimate
the neighboring cell interference in accordance with any of the
embodiments disclosed the unpublished U.S. patent application Ser.
No. 13/488,187, which is incorporated herein (see Appendix A). For
example, the scheduler 14 may be configured to estimate a load
utilization probability p.sub.load(t.sub.1) based at least on a
load utilization probability estimate {circumflex over
(p)}.sub.load(t.sub.0) and an interference-and-noise sum estimate
{circumflex over (P)}.sub.other(t.sub.0)+{circumflex over
(P)}.sub.N(t.sub.0) applicable at a time t.sub.0 to obtain a load
utilization probability estimate {circumflex over
(p)}.sub.load(t.sub.1) applicable at a time t.sub.1, wherein
t.sub.1-t.sub.0=T>0. The scheduler 14 may also be configured to
estimate an interference-and-noise sum
P.sub.other(t.sub.1)+P.sub.N(t.sub.1) based at least on the load
utilization probability estimate {circumflex over
(p)}.sub.load(t.sub.0) and the interference-and-noise sum estimate
{circumflex over (P)}.sub.other(t.sub.0)+{circumflex over
(P)}.sub.N(t.sub.0) to obtain an interference-and-noise sum
estimate {circumflex over (P)}.sub.other(t.sub.1)+{circumflex over
(P)}.sub.N(t.sub.1) applicable at the time t.sub.1. The scheduler
14 may also be configured to estimate a neighbor cell interference
P.sub.other(t.sub.1) based at least on the interference-and-noise
sum estimate {circumflex over (P)}.sub.other(t.sub.1)+{circumflex
over (P)}.sub.N(t.sub.1) and a thermal noise estimate {circumflex
over (P)}.sub.N(t.sub.1) to obtain a neighbor cell interference
estimate {circumflex over (P)}.sub.other(t.sub.1) applicable at the
time t.sub.1. As used here, the load utilization probability
p.sub.load(t) may express a relationship between radio resource
grants scheduled to one or more user equipments, UEs, and radio
resource grants used by the same UEs applicable at a time t. Each
UE may be a UE in the cell of interest, and the load utilization
probability estimate {circumflex over (p)}.sub.load(t) may express
an estimate of the load utilization p.sub.load(t). Furthermore, the
interference-and-noise sum P.sub.other(t)+P.sub.N(t) may express a
sum of undesired signals, other than an own cell load P.sub.own(t),
applicable at the time t, and the interference-and-noise sum
estimate {circumflex over (P)}.sub.other(t)+{circumflex over
(P)}.sub.N(t) being an estimate thereof.
[0114] Also, the own cell load P.sub.own(t) may express a sum of
signals due to wireless activities in the cell of interest
applicable at the time t. Moreover, the neighbor cell interference
P.sub.other(t) may express a sum of interferences present in the
cell of interest due to wireless activities applicable at the time
t in one or more cells other than in the cell of interest, and the
neighbor cell interference estimate {circumflex over
(P)}.sub.other(t) being an estimate thereof. Still further, a
thermal noise P.sub.N(t) may express a sum of undesired signals
present in the cell of interest at the time t other than the own
cell load P.sub.own(t) and other than the neighbor cell
interference P.sub.other(t), and the thermal noise estimate
{circumflex over (P)}.sub.N(t) being an estimate thereof.
[0115] Still further, the scheduler 14 may optionally be configured
to compare an estimated neighboring cell interference with a second
threshold value. If so, the scheduler may be structured to detect
the sudden significant increase in the estimated neighboring cell
interference only in response to the estimated neighboring cell
interference being above the second threshold value. The second
threshold value may e.g. be in the range of 2-4 decibel over a
thermal noise power floor value, i.e. for example 2, 2.5, 3, 3.5 or
4 dB over the thermal noise power floor value.
[0116] The devices, or units, of the radio network node 10 as
illustrated in FIG. 11 need not be implemented strictly in
hardware. It is envisioned that any of the units maybe implemented
through a combination of hardware and software. For example, as
illustrated in FIG. 12, the radio network node 10 may include one
or more central processing units 15 executing program instructions
stored in a storage 16 such as non-transitory storage medium or
firmware (e.g., ROM (Read-Only Memory), RAM (Random-Access Memory),
Flash memory) to perform the functions of the units. The storage 16
may also be referred to as a memory. The radio network node 10 may
also include a transceiver 12 configured to receive wireless
signals from UEs and to send signals to the UEs via one or more
antennas (not shown). The radio network node 10 may further include
a network interface 17 to communicate with other radio network
nodes.
[0117] FIG. 13 illustrates an example embodiment of a second radio
network node 20. The second radio network node 20 may be configured
to perform any of the methods disclosed herein with respect to
FIGS. 6-10. The second radio network node 20 may comprise several
devices, units, modules or circuits. In the illustrated example
embodiment of FIG. 13, the first radio network node 20 comprises a
controller 21, a first transceiver 22, a second transceiver 23 and
a scheduler 24. The transceiver 22 may be configured to wirelessly
communicate with wireless terminals, such as UEs. The transceiver
23 may be configured to communicate with other radio network nodes
and/or with core network nodes. Furthermore, the controller 21 may
be configured to control the overall operations of the radio
network node 20. FIG. 13 provides a logical view of an example
radio network node. It is not strictly necessary that each device,
or unit, is implemented as physically separate devices, units,
modules or circuits. Some or all of the illustrated units may be
implemented in a physical module. Alternatively, one or more units
may be implemented in multiple physical modules as schematically
illustrated in FIG. 14.
[0118] More specifically, and in accordance with one of its
non-limiting aspects, the transceiver 22 may be configured to
transmit and receive messages to and from one or more user
equipments, UEs. Also, the transceiver 23 may be configured to
transmit and receive messages to and from at least one other radio
network node. The transceiver 23 is also configured to receive a
message from said at least one other radio network node, wherein
said message includes an indicator indicating to the second radio
network node that it shall initiate an interference congestion
control procedure. Furthermore, the scheduler 24 is configured to
schedule uplink transmissions from the UEs. Still further, the
scheduler 24 is be configured to, in response to the transceiver 23
receiving said message, analyze the scheduling of one or more user
equipments, UEs, to determine a likelihood that the second radio
network node caused a sudden significant increase in an estimated
neighboring cell interference. Also, the scheduler 24 may be
configured to control uplink interference congestion in dependence
of the determined likelihood that the second radio network node
caused the sudden significant increase in the estimated neighboring
cell interference.
[0119] In one embodiment, the scheduler 24 may be configured to
read a history of uplink, UL, grants for said one or more UEs from
a memory of the second radio network node, wherein the history of
UL grants includes information on the amount of UL grants scheduled
during a second time period. The scheduler 24 may also be
configured to analyze the history of UL grants to determine whether
an increase of the amount of scheduled UL grants has occurred
during said second time period. If it is determined that an
increase of the amount of UL grants has occurred during said second
time period, the scheduler 24 is also configured to compare the
detected increase of the amount of scheduled UL grants with a third
threshold value, and also control the UL interference congestion if
the detected increase of the amount of scheduled UL grants is above
the third threshold. The length of the second time period may be in
the range of 10 to 80 milliseconds. That is, the length of the
second time period may e.g. be 10, 15, 20, 25, 30, 35, 40, 45, 50,
55, 60, 65, 70, 75 or 80 milliseconds. Also, the third threshold
value may be a value which is in the range of 30-60 percent of the
maximum amount of scheduled UL grants that can be assigned by the
second radio network node.
[0120] Additionally, or alternatively, the scheduler 24 may be
configured to read a history of transmit powers of said one or more
UEs from a memory of the second radio network node, wherein the
history of transmit powers includes information on the transmit
powers of said one or more UEs during a third time period. The
scheduler 24 may also be configured to analyze the history of
transmit powers to determine whether an increase of transmit powers
has occurred during said third time period. If it is determined
that an increase of the transmit powers has occurred during said
third time period, the scheduler 24 may be further configured to
compare the detected increase of the transmit powers with a fourth
threshold value; and also control the UL interference congestion if
the detected increase of the transmit powers is above the fourth
threshold. The length of the third time period may be in the range
of 10 to 80 milliseconds. That is, the length of the second time
period may e.g. be 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,
70, 75 or 80 milliseconds. Also, the fourth threshold value is a
value which is in the range of 5-15 decibel. For example, the
fourth threshold value may be 5, 10 or 15 db.
[0121] In some embodiments, the scheduler 24 is configured to
control the UL interference congestion by transmitting, by means of
transceiver 22, a message to one or more UEs, wherein said message
comprises an information element including a request to the one or
more UEs to decrease the allowable UL data rate. In some
embodiments, the scheduler 24 is configured to control the UL
interference congestion by transmitting, by means of transceiver
22, a message to one or more UEs, wherein said message comprises an
information element including a request to the one or more UEs to
reduce the transmission power.
[0122] The units of the radio network node 20 as illustrated in
FIG. 13 need not be implemented strictly in hardware. It is
envisioned that any of the units maybe implemented through a
combination of hardware and software. For example, as illustrated
in FIG. 14, the radio network node 20 may include one or more
central processing units 15 executing program instructions stored
in a storage (e.g. memory) 16 such as non-transitory storage medium
or firmware (e.g., ROM, RAM, Flash) to perform the functions of the
units. The radio network node 10 may also include a transceiver 12
configured to receive wireless signals from UEs and to send signals
to the UEs via one or more antennas (not shown). The radio network
node 10 may further include a network interface 17 to communicate
with other radio network nodes.
[0123] It should be appreciated that a single radio network node
may implement the functionality as described hereinabove with
respect to both the first radio network node 10 and the second
radio network node 20, respectively. Consequently, a radio network
node may comprise devices, units, modules or circuits of the first
radio network node 10 as well as the second radio network node
20.
[0124] According to some embodiments, the first radio network node
10 may be embodied as a RBS, e.g. a NodeB. In other embodiments,
the first radio network node 10 may be embodied as a Radio Network
Controller (RNC).
[0125] Similarly, the second radio network node 20 may be embodied
as a RBS, e.g. a NodeB. In other embodiments, the second radio
network node 20 may be embodied as a RNC. Thus, there exist various
alternatives, such as for example the following: [0126] The first
radio network node 10 may be a RBS and the second radio network
node 20 may be a RBS (utilizing signaling over an lub interface or
a proprietary interface to the RNC, then from the RNC to the second
radio network node over lub or over a proprietary interface).
[0127] The first radio network node 10 may be a RBS and the second
radio network node 20 may be a RBS (e.g. utilizing signaling over a
proprietary interface, lubx interface).
[0128] The embodiments disclosed herein are also conceivable in
LTE. If implemented in LTE, the first and second radio network
nodes 10, 20 may be implemented as evolved NodeB's (eNB's). If so
the signaling can be over the X2 interface between the eNB's.
[0129] In the detailed description hereinabove, for purposes of
explanation and not limitation, specific details are set forth in
order to provide a thorough understanding of various embodiments
described in this disclosure. In some instances, detailed
descriptions of well-known devices, units, modules, components,
circuits, and methods have been omitted so as not to obscure the
description of the embodiments disclosed herein with unnecessary
detail. All statements herein reciting principles, aspects, and
embodiments disclosed herein, as well as specific examples thereof,
are intended to encompass both structural and functional
equivalents thereof. Additionally, it is intended that such
equivalents include both currently known equivalents as well as
equivalents developed in the future, i.e., any elements developed
that perform the same function, regardless of structure. Thus, for
example, it will be appreciated that block diagrams herein can
represent conceptual views of illustrative circuitry or other
functional units embodying the principles of the embodiments.
Similarly, it will be appreciated that any flow charts and the like
represent various processes which may be substantially represented
in computer readable medium and so executed by a computer or
processor, whether or not such computer or processor is explicitly
shown. The functions of the various elements including functional
blocks, may be provided through the use of hardware such as circuit
hardware and/or hardware capable of executing software in the form
of coded instructions stored on computer readable medium. Thus,
such functions and illustrated functional blocks are to be
understood as being either hardware-implemented and/or
computer-implemented, and thus machine-implemented. In terms of
hardware implementation, the functional blocks may include or
encompass, without limitation, digital signal processor (DSP)
hardware, reduced instruction set processor, hardware (e.g.,
digital or analog) circuitry including but not limited to
application specific integrated circuit(s) [ASIC], and/or field
programmable gate array(s) (FPGA(s)), and (where appropriate) state
machines capable of performing such functions. In terms of computer
implementation, a computer is generally understood to comprise one
or more processors or one or more controllers. When provided by a
computer or processor or controller, the functions may be provided
by a single dedicated computer or processor or controller, by a
single shared computer or processor or controller, or by a
plurality of individual computers or processors or controllers,
some of which may be shared or distributed. Moreover, use of the
term "processor" or "controller" shall also be construed to refer
to other hardware capable of performing such functions and/or
executing software, such as the example hardware recited above.
[0130] Although the various embodiments of this disclosure have
been described above with reference to specific embodiments, it is
not intended to be limited to the specific form set forth herein.
The embodiments of this disclosure are limited only by the
accompanying claims and other embodiments than the specific above
are equally possible within the scope of the appended claims. As
used herein, the terms "comprise/comprises" or "include/includes"
do not exclude the presence of other elements or steps.
Furthermore, although individual features may be included in
different claims, these may possibly advantageously be combined,
and the inclusion of different claims does not imply that a
combination of features is not feasible and/or advantageous. In
addition, singular references do not exclude a plurality. Finally,
reference signs in the claims are provided merely as a clarifying
example and should not be construed as limiting the scope of the
claims in any way.
* * * * *